Proposal The goal of this proposal is to further characterize the subunits which comprise the basal transcription factor BTF2. These investigations will define the role of each subunit, the domains necessary for catalytic activity, protein-protein interactions and the minimal complex required to support transcription, nucleotide excision repair (NER) and activation of p34cdc2. Approach Aim 1. Develop a reconstituted system for analysis of recombinant BTF2 subunits. Aim 2. Identify complex(es) which function in vitro to activate transcription, NER and p34cdc2 Aim 3. Define subunit domains which control protein interactions and specific functions Aim 4. Demonstrate a requirement, in vivo, for individual subunits in functional complexes of BTF2. Significance Humans with mutations in subunits of BTF2 exhibit several DNA repair disorders such as xeroderma pigmentosum, Cockayne's syndrome and trichothiodystrophy. These diseases are characterized by extreme sensitivity o UV light and result in several types of malignancies as well as neurological and developmental disorders. 21. Description Continued: (Hoeijmakers 1993). Understanding how mutations in BTF2 subunits alter complex function in transcription and NER at the molecular level is an important step in correction and treatment of these illnesses.